A compatible series of large microdata samples of census and survey data spanning the period from 1850 to the present. IPUMS reduces costs for the population and health research community by minimizing redundant effort, simplifying data access, increasing the replicability of studies, and improving data reliability. The availability o large-scale integrated microdata has opened extraordinary new opportunities for fine-grained contextual analyses of processes of change, resulting in transformational research across a diverse range of topics and disciplines. Over the past five years, IPUMS has seen explosive growth in the number of researchers using the database, the amount of data they request, and the number of high-impact publications they produce. At the same time, however, there is unprecedented demand from researchers for expansion, improvement, and support of the infrastructure. This project will undertake four major activities to meet this demand: 1. Database expansion. The quantity of U.S. data supported by IPUMS will double over the coming five years to include 775 harmonized datasets describing the characteristics of approximately 500 million persons. 2. Data and metadata improvement. The project will undertake a series of activities to improve documentation and make it more accessible, correct data errors, provide innovative tools for spatial analysis, and develop new integrated variables describing families and occupations. 3. Data infrastructure and access. The underlying infrastructure supporting the IPUMS data collection will be redesigned using column-store data structures, a novel toolset to simplify metadata creation and maintenance, and new tools to simplify data manipulation and reduce redundant effort by researchers. 4. Dissemination and sustainability. IPUMS Redesign will continue to provide user support, training, and outreach, and will also implement new strategies to harness the expertise of the IPUMS user community to promote collaboration and scientific discovery. To ensure preservation over multiple decades, the project will develop and implement a new preservation plan. This infrastructure is a basic resource for health research and policy analysis. Models and descriptions of the past underlie both theories of past social change and projections into the future. Accordingly, the data series provides a unique laboratory for the study of health and demographic processes, and provides the empirical foundation we need for developing and testing social and economic models.